Peters Bram B C, Zheng Jia, Krajangsri Suppachai, Andersson Pher G
Department of Organic Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691Stockholm, Sweden.
School of Chemistry and Physics, University of Kwazulu-Natal, Private Bag X54001, 4000Durban, South Africa.
J Am Chem Soc. 2022 May 18;144(19):8734-8740. doi: 10.1021/jacs.2c02422. Epub 2022 May 5.
Asymmetric hydrogenation of prochiral substrates such as ketones and olefins constitutes an important instrument for the construction of stereogenic centers, and a multitude of catalytic systems have been developed for this purpose. However, due to the different nature of the π-system, the hydrogenation of olefins and ketones is normally catalyzed by different metal complexes. Herein, a study on the effect of additives on the Ir-N,P-catalyzed hydrogenation of enones is described. The combination of benzamide and the development of a reactive catalyst unlocked a novel reactivity mode of Crabtree-type complexes toward C═O bond hydrogenation. The role of benzamide is suggested to extend the lifetime of the dihydridic iridium intermediate, which is prone to undergo irreversible trimerization, deactivating the catalyst. This unique reactivity is then coupled with C═C bond hydrogenation for the facile installation of two contiguous stereogenic centers in high yield and stereoselectivity (up to 99% , 99/1 d.r.) resulting in a highly stereoselective reduction of enones.
前手性底物（如酮和烯烃）的不对称氢化是构建手性中心的重要手段，为此已开发出多种催化体系。然而，由于π-体系的性质不同，烯烃和酮的氢化通常由不同的金属配合物催化。本文描述了添加剂对Ir-N,P催化烯酮氢化反应影响的研究。苯甲酰胺与活性催化剂的结合开启了Crabtree型配合物对C═O键氢化的新型反应模式。苯甲酰胺的作用被认为是延长二氢铱中间体的寿命，该中间体容易发生不可逆的三聚反应，使催化剂失活。然后，这种独特的反应性与C═C键氢化相结合，能够以高收率和立体选择性（高达99%，99/1的非对映体比例）轻松构建两个相邻的手性中心，从而实现烯酮的高度立体选择性还原。
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